param( 
    [string]$url
)

function GetWebSizes ($startWeb)
{
        $web = Get-SPWeb $startWeb
        [long]$total = 0
        $total += GetWebSize -Web $web
        $total += GetSubWebSizes -Web $web
        $totalInMb = ($total/1024)/1024
        $totalInMb = "{0:N2}" -f $totalInMb
        $totalInGb = (($total/1024)/1024)/1024
        $totalInGb = "{0:N2}" -f $totalInGb
        Write-Host "Total size of all sites below" $startWeb "is" $total "Bytes,"
        Write-Host "which is" $totalInMb "MB or" $totalInGb "GB"
        $web.Dispose()
}
 
function GetWebSize ($web)
{
	[long]$subTotal = 0
	foreach ($folder in $web.Folders)
	{
		$subTotal += GetFolderSize -Folder $folder
	}

	Write-Host "Site" $web.Title "is" $subTotal "KB"
	return $subTotal
}
 
function GetSubWebSizes ($web)
{
	[long]$subTotal = 0
	foreach ($subweb in $web.GetSubwebsForCurrentUser())
	{
		[long]$webtotal = 0
		foreach ($folder in $subweb.Folders)
		{
			$webtotal += GetFolderSize -Folder $folder
		}
		Write-Host "Site" $subweb.Title "is" $webtotal "Bytes"
		$subTotal += $webtotal
		$subTotal += GetSubWebSizes -Web $subweb
	}
	return $subTotal
}
 
function GetFolderSize ($folder)
{
	[long]$folderSize = 0 
	foreach ($file in $folder.Files)
	{
		$folderSize += $file.Length;
	}
	foreach ($fd in $folder.SubFolders)
	{
		$folderSize += GetFolderSize -Folder $fd
	}
	return $folderSize
}

if (-not $url)
{
    Write-Host "Specify site url in url parameter" -foregroundcolor red
    return
}

GetWebSizes $url